1. Field of the Invention
The present invention relates to an optical switch, and particularly to an optical switch which achieves switching operation by employing a piezoelectric device to control the movement of a crystal element thereof.
2. Description of Related Art
A typical optical switch has one or more light input port(s) and at least two light output ports for performing switching or logical operations to optical signals in a light transmitting line/system or in an integrated optical circuit. Factors for assessing the capability of an optical switch include low insertion loss (IL,  less than 1 db), good isolation performance ( greater than 50 db), and fast switching speed (normally, tens of milliseconds).
One elementary kind of the traditional mechanical switches is operated by moving an input fiber relative to a plurality of output fibers. An example of the conventional design is disclosed in U.S. Pat. Nos. 4,303,302 and 4,896,935. However, these conventional optical switches share a common problem of requiring high precision parts to obtain precise positioning control and low insertion loss. This results in high costs and complicates manufacture of the switches. Moreover, frequently moving fibers to and fro is apt to damage or even break the fibers.
Another traditional mechanical optical switch realizes its switching function by moving optical elements, such as sleeves, collimating members and reflectors, between light input and output ports. FIGS. 1 and 2 show an example of an optical switch of this type disclosed in U.S. Pat. No. 4,705,349. A switch 10 comprises a mounting fixture 12, optical fibers 14, 16 and 18, a rotatable table 32 and a planar reflector 36. The reflector 36 is mounted on the rotating substrate 32 to be moveable therewith. Light from fibers 14, 16 is selectively directed by the reflector 36 into the fiber 18 by rotating the rotatable table 32. A setting screw 38 is used for precise positioning of the rotatable stable 32. Due to possible fatigue during operation, the arrangement is not very reliable. In addition, a spring device (not shown in FIGS. 1 and 2) is adopted to drive the rotatable table 32, resulting in a slow switching speed. Furthermore, such a design inevitably has disadvantages as high costs and complicated manufacture requirements.
An object of the present invention is to provide an optical switch employing crystal members as its transmitting medium thereby obtaining a low insertion loss thereof.
Another object of the present invention is to provide an optical switch having a high switching speed by adopting a piezoelectric device to control light paths of the switch.
In accordance with one aspect of the present invention, an optical switch comprises a fixed first crystal element having a first surface, a movable second crystal element sharing the same refracting index with the first crystal element and having a second surface corresponding to the first surface of the first crystal element, and a driving device for driving the second crystal element to move relative to the first crystal element between first and second positions. The driving device comprises a piezoelectric element.
In the first position, the second surface of the second crystal element abuts against the first surface of the first crystal element, allowing a light beam transmitting into the first crystal element to pass through the second crystal element without substantial reflection.
In the second position, a gap is formed between the first surface and the second surface of the first and second crystal elements whereby a light beam transmitting into the first crystal element is fully reflected on the first surface and no longer passes the second crystal element. Thus, the light beam leaves the switch in different directions, achieving a switching operation.
Guiding members are positioned on opposite sides of the second crystal element to guide the movement thereof. At least one of the guiding members has a pair of spaced arms extending from a base with a space defined therebetween. Slots are defined in opposing edges of the arms for receiving and thus guiding the second crystal element.